The present invention relates in general to a device for handling coking coal, and in particular to a device for drying and preheating coking coal in a turbulent layer by means of an indirect heat exchange with a heating medium.
A device of this kind is known from German patent publication No. 2 342 184, in which steam is employed both as heating medium and as a medium for producing a fluidized bed of the coal. The drying and the preheating of the coal to a temperature above 150.degree. C. in this prior-art device is made in a single stage. As a consequence, a very intensive heat supply is necessary. It has been found, however, that such an excessive exposure to heat is disadvantageous for the condition of the treated coal. For example, in this prior-art device coal is prone to cake together or to bake on the heating pipes. In addition, local overheating of coal particles may occur, resulting in undesirable changes of the coking quality of the coal.